Assembly mechanism and energy transfer pathways of plant photosystem II-LHCII supercomplexes discovered through cryo-electron microscopy

Funded by the National Natural Science Foundation of China,Chinese Ministry of Science and Technology,and Chinese Academy of Sciences,ajoint team of three laboratories from the Institute of Biophysics of Chinese Academy of Sciences,namely Liu Zhenfeng’s(柳振峰),Zhang

Respiratory supercomplexes:structure,function and assembly

The mitochondrial respiratory chain consists of 5 enzyme complexes that are responsible for ATP generation.The paradigm of the electron transport chain as discrete enzymes diffused in the inner mitochondrial membrane has been replaced by the solid state supercomplex model wherein the respiratory complexes associate with each other to form supramolecular complexes.Defects in these supercomplexes,which have been shown to be functionally active and required for forming stable respiratory complexes,have been associated with many genetic and neurodegenerative disorders demonstrating their biomedical signifi cance.In this review,we will summarize the functional and structural signifi cance of supercomplexes and provide a comprehensive review of their assembly and the assembly factors currently known to play a role in this process.

3D Fractals, Axiom of Algebra (Δn)n = +1

After having laid down the Axiom of Algebra, bringing the creation of the square root of -1 by Euler to the entire circle and thus authorizing a simple notation of the nth roots of unity, the author uses it to organize homogeneous divisions of the limited development of the exponential function, that is opening the way to the use of a whole bunch of new primary functions in Differential Calculus. He then shows how new supercomplex products in dimension 3 make it possible to calculate fractals whose connexity depends on the product considered. We recall the geometry of convex polygons and regular polygons.

Clifford Algebra and Hypercomplex Number as well as Their Applications in Physics

The Clifford algebra is a unification and generalization of real number, complex number, quaternion, and vector algebra, which accurately and faithfully characterizes the intrinsic properties of space-time, providing a unified, standard, elegant, and open language and tools for numerous complicated mathematical and physical theories. So it is worth popularizing in the teaching of undergraduate physics and mathematics. Clifford algebras can be directly generalized to 2n-ary associative algebras. In this generalization, the matrix representation of the orthonormal basis of space-time plays an important role. The matrix representation carries more information than the abstract definition, such as determinant and the definition of inverse elements. Without this matrix representation, the discussion of hypercomplex numbers will be difficult. The zero norm set of hypercomplex numbers is a closed set of special geometric meanings, like the light-cone in the realistic space-time, which has no substantial effect on the algebraic calculus. The physical equations expressed in Clifford algebra have a simple formalism, symmetrical structure, standard derivation, complete content. Therefore, we can hope that this magical algebra can complete a new large synthesis of modern science.

The immunophilin CYCLOPHILIN28 affects PSII-LHCII supercomplex assembly and accumulation in Arabidopsis thaliana

In plant chloroplasts,photosystem II(PSII)complexes,together with light-harvesting complex II(LHCII),form various PSII-LHCII supercomplexes(SCs).This process likely involves immunophilins,but the underlying regulatory mechanisms are unclear.Here,by comparing Arabidopsis thaliana mutants lacking the chloroplast lumen-localized immunophilin CYCLOPHILIN28(CYP28)to wildtype and transgenic complemented lines,we determined that CYP28 regulates the assembly and accumulation of PSII-LHCII SCs.Compared to the wild type,cyp28 plants showed accelerated leaf growth,earlier flowering time,and enhanced accumulation of high molecular weight PSII-LHCII SCs under normal light conditions.The lack of CYP28 also significantly affected the electron transport rate.Blue native-polyacrylamide gel electrophoresis analysis revealed more Lhcb6 and less Lhcb4 in M-LHCII-Lhcb4-Lhcb6 complexes in cyp28 versus wild-type plants.Peptidyl-prolyl cis/trans isomerase(PPIase)activity assays revealed that CYP28 exhibits weak PPIase activity and that its K113 and E187 residues are critical for this activity.Mutant analysis suggested that CYP28 may regulate PSIILHCII SC accumulation by altering the configuration of Lhcb6 via its PPIase activity.Furthermore,the Lhcb6-P139 residue is critical for PSII-LHCII SC assembly and accumulation.Therefore,our findings suggest that CYP28 likely regulates PSII-LHCII SC assembly and accumulation by altering the configuration of P139 of Lhcb6 via its PPIase activity.

你的心头也有星辰大海——带你领略呼吸的奥秘

呼吸作用是最基本的生命活动之一.20世纪初,科学家们发现了一系列可以进行电子传递的铁硫中心、卟啉环等辅基,而后又逐步鉴定出这些辅基固定在一系列的蛋白质复合物中.最近,人们发现这些蛋白质复合物并不是相互独立存在的,而是倾向于结合在一起形成呼吸体.

Coevolution study of mitochondria respiratory chain proteins:Toward the understanding of protein-protein interaction

Coevolution can be seen as the interdependency between evolutionary histories. In the context of protein evolution, functional correlation proteins are ever-present coordinated evolutionary characters without disruption of organismal integrity. As to complex system, there are two forms of protein-protein interactions in vivo, which refer to inter-complex interaction and intra-complex interaction. In this paper, we studied the difference of coevolution characters between inter-complex interaction and intra-complex interaction using ＂Mirror tree＂ method on the respiratory chain （RC） proteins. We divided the correlation coefficients of every pairwise RC proteins into two groups corresponding to the binary protein--protein interaction in intra-complex and the binary protein--protein interaction in inter-complex, respectively. A dramatical discrepancy is detected between the coevolution characters of the two sets of protein interactions （Wilcoxon test, p-value = 4.4 × 10 6）. Our finding reveals some critical information on coevolutionary study and assists the mechanical investigation of protein-protein interaction. Furthermore, the results also provide some unique clue for supramolecular organization of protein complexes in the mitochondrial inner membrane. More detailed binding sites map and genome information of nuclear encoded RC proteins will be extraordinary valuable for the further mitochondria dynamics study.

Dynam,c Changes of IsiA-Containing Complexes during Long-Term Iron Deficiency in Synechocystis sp, PCC 6803

Iron stress-induced protein A （IsiA）, a major chlorophyll-binding protein in the thylakoid membrane, is significantly induced under iron deficiency conditions. Using immunoblot analysis and 77 K fluorescence spectroscopy combined with sucrose gradient fractionation, we monitored dynamic changes of IsiA- containing complexes in Synechocystis sp. PCC 6803 during exposure to long-term iron deficiency. Within 3 days of exposure to iron deficiency conditions, the initially induced free IsiA proteins preferentially con- jugated to PSI trimer to form IsiA18-PS I trimers, which serve as light energy collectors for efficiently trans- mitting energy to PS h With prolonged iron deficiency, IsiA proteins assembled either into IsiA aggregates or into two other types of IsiA-PS I supercomplexes, namely IsiA-PS I high fluorescence supercomplex （IHFS） and IsiA-PS I low fluorescence supercomplex （ILFS）. Further analysis revealed a role for IsiA as an energy dissipater in the IHFS and as an energy collector in the ILFS. The trimeric structure of PS I mediated by PsaL was found to be indispensable for the formation of IHFS/ILFS. Dynamic changes in IsiA-containing complexes in cyanobacteria during long-term iron deficiency may represent an adaptation to iron limitation stress for flexible light energy distribution, which balances electron transfer between PS I and PS II, thus minimizing photooxidative damage.

Research journey of respirasome

Respirasome,as a vital part of the oxidative phosphorylation system,undertakes the task of transferring electrons from the electron donors to oxygen and produces a proton concentration gradient across the inner mitochondrial membrane through the coupled translocation of protons.Copious research has been carried out on this lynchpin of respiration.From the discovery of individual respiratory complexes to the report of the high-resolution structure of mammalian respiratory supercomplex I1III2IV1,scientists have gradually uncovered the mysterious veil of the electron transport chain(ETC).With the discovery of the mammalian respiratory mega complex I2III2IV2,a new perspective emerges in the research field of the ETC.Behind these advances glitters the light of the revolution in both theory and technology.Here,we give a short review about how scientists‘see’the structure and the mechanism of respirasome from the macroscopic scale to the atomic scale during the past decades.

Molecular studies of cellulose synthase supercomplex from cotton fiber reveal its unique biochemical properties

Cotton fiber is a highly elongated and thickened single cell that produces large quantities of cellulose,which is synthesized and assembled into cell wall microfibrils by the cellulose synthase complex(CSC).In this study,we report that in cotton(Gossypium hirsutum)fibers harvested during secondary cell wall(SCW)synthesis,GhCesA 4,7,and 8 assembled into heteromers in a previously uncharacterized 36-mer-like cellulose synthase supercomplex(CSS).This super CSC was observed in samples prepared using cotton fiber cells harvested during the SCW synthesis period but not from cotton stem tissue or any samples obtained from Arabidopsis.Knock-out of any of GhCesA 4,7,and 8 resulted in the disappearance of the CSS and the production of fiber cells with no SCW thickening.Cotton fiber CSS showed significantly higher enzyme activity than samples prepared from knock-out cotton lines.We found that the microfibrils from the SCW of wild-type cotton fibers may contain 72 glucan chains in a bundle,unlike other plant materials studied.GhCesA4,7,and 8 restored both the dwarf and reduced vascular bundle phenotypes of their orthologous Arabidopsis mutants,potentially by reforming the CSC hexamers.Genetic complementation was not observed when non-orthologous CesA genes were used,indicating that each of the three subunits is indispensable for CSC formation and for full cellulose synthase function.Characterization of cotton CSS will increase our understanding of the regulation of SCW biosynthesis.

Carotenoid metabolism in mitochondrial function

Mitochondria are highly dynamic organelles that are found in most eukaryotic organisms.It is broadly accepted that mitochondria originally evolved from prokaryotic bacteria,e.g.proteobacteria.The mitochondrion has its independent genome that encodes 37 genes,including 13 genes for oxidative phosphorylation.Accumulative evidence demonstrates that mitochondria are not only the powerhouse of the cells by supplying adenosine triphosphate,but also exert roles as signalling organelles in the cell fate and function.Numerous factors can affect mitochondria structurally and functionally.Carotenoids are a large group of fat-soluble pigments commonly found in our diets.Recently,much attention has been paid in carotenoids as dietary bioactives in mitochondrial structure and function in human health and disease,though the mechanistic research is limited.Here,we update the recent progress in mitochondrial functioning as signalling organelles in human health and disease,summarize the potential roles of carotenoids in regulation of mitochondrial redox homeostasis,biogenesis,and mitophagy,and discuss the possible approaches for future research in carotenoid regulation of mitochondrial function.

Assembly mechanisms and energy transfer pathways deciphered in the cryo-EM structure of spinach photosystem Ⅱ-LHCⅡ supercomplex

Funded by the National Natural Science Foundation of China(NSFC),Ministry of Science and Technology of China,and Chinese Academy of Sciences,ajoint team of three laboratories from the Institute of Biophysics of Chinese Academy of Sciences,led by Dr.Liu Zhenfeng(柳振峰),Dr.Zhang Xinzheng(章新政)and Dr.Li Mei(李梅)respectively,solved the structure of spinach photosystem II-LHCII supercom-